Monday, 25 March 2019

How bidirectional cycle-paths improve cycling safety and efficiency

Imagine if sidewalks (pavements in the UK) for pedestrians were unidirectional. If you wanted to visit your neighbour who lived on the right side of your home then you could walk there directly, but to come back home again in a legal manner you'd be expected to cross the road, walk until you were opposite your home and then cross back again. Does that make sense ? Of course not. The inconvenience of expecting people to cross the road simply to walk in the opposite direction is absurd. All sidewalks are therefore bidirectional.

Bidirectional cycle-paths, well implemented, provide cyclists with a similar level of utility as do bidirectional sidewalks. Instead of having to cross a road to travel a short distance in the "wrong" direction, cyclists can stay on the same side of a road. This makes short journeys significantly faster. It also improves their safety because they don't have to cross the road twice. Crossing the road is a significant risk: I noted in a previous blog that the most dangerous locations for cyclists in many Dutch cities are often simple uncontrolled crossings (at least where more dangerous examples of infrastructure have been eliminated)

Directness of routes is important for cycling to succeed. The more efficient that we can make cycling, the more journeys there are for which people will find it a convenient mode of transport. Bidirectional cycle-paths allow for this convenience.

It is, of course, possible to create a poor version of almost anything. That includes bidirectional cycle-paths. Where they are criticised, look for other issues. For example, poor junction design which may create conflict or make cyclists less visible to drivers.

Here are some examples of where bidirectional cycle-paths make sense. Click on the links in the descriptions of the photos to see more examples:

In a city centre
In the city centre, where a cycle-path replaced a busy road, only a bidirectional cycle-path makes sense

In the countryside

Cycle-paths through recreational areas are almost always bidirectional. There would be no sense in making them otherwise. 

Alongside a busy road
This bidirectional cycle-path is alongside a busy road through an industrial area which has four lanes of motor traffic, a central reservation and destinations on both sides. It is not desirable to require people to cross the road than is absolutely necessary. Bidirectional cycling is possible on both sides of the road.
in residential areas
This bidirectional cycle-path is in a residential suburb. In this case there is a canal on the other side of the road so it would make no sense at all to require cyclists to cross the road in order to ride next to the canal instead of next to the homes which are destinations for cyclists.
Brand new infrastructure linking a residential area to the centre of the city. There is a road behind the bushes on the right, but after the road there is nothing but the railway track. Here also it makes sense for cyclists to ride on one side of the road in both directions.

Where all destinations are on one side of the road
All destinations along this road, including shops and cafes, are on this side of road while on the other side of the road there is a canal. It would make no sense here to make cyclists cross in order to ride towards the camera. On the other side of the canal there is a bidirectional bicycle road which does not offer a through route to drivers. Note also how the road junction design reduces the danger of collision with motor vehicles. The turning radius is small and the black "cannonballs" prevent drivers from cutting the corner.
Roundabout design
One of several features which defines the safest urban roundabout design for cyclists is a design which allows safe use of bidirectional cycle-paths. These also increase convenience by allowing so few crossings to be made as possible (you are never required to ride across three arms of a roundabout to turn across traffic).

Traffic light design
Simultaneous Green traffic light junction. Cyclists can go in all directions at once when the lights are green for bikes. All motor vehicles are held behind red lights and all possibility of conflict with them is removed. A very useful design for use with bidirectional cycle-paths. Also note the width of the cycle-path, which can cope with large flows of cyclists. Also see a different traffic light design which feeds into a bidirectional cycle-path without conflict.

Through tunnels
Cycle-paths through tunnels are nearly always bidirectional. Otherwise we would require two tunnels. Tunnels are generally preferable to bridges for cyclists.

Bicycle roads
This bicycle road is on the other side of the canal from the last photo. Bicycle roads are of course always bidirectional for cyclists, though they are sometimes one-way for drivers.
Where a bicycle road ends and cycle traffic is led onto a cycle-path it would be absurd to use anything other than a bidirectional cycle-path such as is shown here. In this case there are some recreational destinations on the right of the road, but the vast majority of destinations (homes and shops) are on the left, and are served well by this cycle-path. 
Adequate width for tidal flow or at junctions between cycle-paths
Just short of four metres wide, this cycle-path copes well with considerable cycling volumes, especially tidal traffic at school times (the low building behind the cyclists to the right is a secondary school). Behind the camera there is a busy road junction.

Junctions between cycle-paths require even more width. At this point, the cycle-path exceeds six metres in width. The bridges cross a canal.
We sometimes hear blanket criticism of the idea of bidirectional cycle-paths, but it is not justified. In many cases they improve both safety and convenience for cyclists. To a first approximation a bidirectional cycle-path is always more useful than a single-direction path for the simple reason that cyclists can use it in both directions.


Unknown said...

This is a very helpful post. I always though this cycle track in St Kilda (Melbourne) was bad, but with your insights it's possible to identify such issues as:
* unnecessary dangerous crossings (compared to other side of the street with fewer and lower volume intersections)
* on the wrong side of the street to access destinations
* too narrow

Ian Perry (Cardiff, UK) said...

How wide are these bi-directional pathways?

David Hembrow said...

Ian: Those in the photos in this blog post vary from 3 m wide to 6 m wide. Three metres is a bit too narrow. 3.5 m and upwards generally works well. But 3 m on both sides of the road usually also works well because the usage is spread between both paths. There's another blog post about widths (including why these widths are important).

Oscar Newman said...

Hi David,

Thanks for your blog, I greatly enjoy reading your posts.

I know from your previous posts that you also think infrastructure should adapt to human nature or instinct, rather than the other way around. I have a question I wonder whether your experience could shed some light on.

In Dublin there are very few dedicated cycle paths. Where they do exist they are of course a single narrow lane - either unidirectional beside a road, or a vague mixture of pedestrians and cyclists (e.g. the "before" image is how it looks now: this is a busy bidirectional cycle and pedestrian commuter path

What I find curious is that when I encounter oncoming cyclists, they usually wish to pass on the right. This sometimes leads to absurd and dangerous situations as we are forced to brake and I inevitably give way and swerve to their right. I have had people cursing me for cycling head-on into them, attempting to pass on the left. You are I'm sure aware than traffic in Ireland is left-hand as in the UK. I cannot relinquish my intent to pass on the left as 99% of my cycling here is on the road, necessarily.

Cycling is still very much a niche pursuit here. I speculate that many cycle out of poverty rather than choice. They cannot afford to be drivers and such have not been conditioned to pass on the left. Related, maybe a larger proportion of cyclists are immigrants from right-hand drive countries who are not sufficiently established to own a car.

I wonder if you have any idea what cues people are using to pass on the right and why I am oblivious to them.

David Hembrow said...

Oscar: IMO you're doing the right thing by riding on the left, whether you're on a road or a cycle-path. I really don't know why people would think they should do the opposite when they ride a bike. It's not something I've come across. Perhaps they're confused by the idea that pedestrians should walk on the "wrong" side of roads so that they can see oncoming traffic ?

Ian Perry (Cardiff, UK) said...

Needless to say, I'm looking at 2.5m wide, unbuffered, shared paths here in Wales being built today... And then there is worse...